1. Field of the Invention
This invention relates to method and apparatus for supporting a rock formation and, more particularly, to a bearing plate having an embossed configuration complementary with embossments on a channel member for exerting a compressive force on the rock formation.
2. Description of the Prior Art
In underground mining, excavation and tunnelling operations, it is conventional practice to support the overhead and lateral rock strata by elongated structural members, such as metal roof mats and channels, that extend transversely across the mine roof and downwardly along the lateral sidewalls or ribs. The mats and channels are provided in various lengths with holes spaced a preselected distance apart through the members to conform to a conventional roof bolt plan. Roof bolts extend through the holes in the channels and into holes drilled in the rock strata and are anchored in the strata to maintain the channels compressed against the surface of the rock strata. The metal mats and channels are preferably used in place of wood timbers and are more efficiently installed in combination with a roof bolting system.
U.S. Pat. No. 2,192,554 discloses an improvement over wood timbering structures in which concrete roof beams are supported in contact with a mine tunnel roof by horizontal metal props connected at their end portions to vertical props. The vertical props extend to the mine floor oppositely the mine rib or wall. This arrangement forms a truss of interlocking parts for reinforcing the roof beams. U.S. Pat. No. 3,413,812 is another example of elongated beam members connected to one another for supporting an underground rock formation.
It is also known to utilize elongated members that overlap at their end portions to form a sliding joint in an arc-type support. Examples of interconnected trough-shaped sections for supporting a rock formation are disclosed in U.S. Pat. Nos. 3,023,862; 3,076,672; 3,126,708 and 3,168,815.
U.S. Pat. No. 3,022,100 discloses an arc support formed by three sections that overlap at their end portions. U.S. Pat. No. 3,395,542 discloses a propping frame having two upright members for supporting interconnecting members forming an arc.
As indicated above, it is common practice to utilize elongated mats and channels as part of a mine roof bolt plan. In a conventional roof bolt plan, bore holes are drilled into the rock formation in accordance with a preselected pattern so that the bolts are positioned a preselected distance apart and extend a preselected depth into the rock formation. The roof bolts are anchored in the bore holes and tensioned to exert a compressive force upon the rock strata to prevent deterioration of the overhead rock strata.
It is also conventional practice in the installation of mine roof bolts to use bearing plates to support the area of the rock formation around the bore hole. A conventional bearing plate includes a contact or bearing surface for abutting the formation around the bore hole. The bearing plate includes a central hole for receiving a roof bolt which extends through the plate up into the bore hole. The lower end of the roof bolt includes an enlarged head which bears against the area of the plate around the bore hole. To rigidify bearing plates to resist deflection and bending when compressed against the rock formation, bearing plates are provided with embossments which extend from the surfaces of the bearing plates. Examples of known bearing plates having embossments are disclosed in U.S. Pat. Nos. 2,748,594; 2,854,824; 3,090,203; 3,226,934; 3,238,731; 3,478,523; 4,037,418; and 4,249,835 and French Patent Nos. 1,222,640 and 1,304,298.
The bearing plates can be used With or without mat or channel supports. When used with mats and channels, the bearing plate is positioned in overlying relation with the channel so that the opening of the channel is aligned with the opening in the roof plate. In one method, the roof plate used with a mat or channel has a width equal to the width of the channel and a length to be received within the elongated slot of the channel. In the alternative, the surface of the bearing plate extends beyond the channel slot and bears against the areas of the channel around the slot.
Because of the extended length of the mat or channel, it is subject to deflection and bending when anchored by the roof bolts into compressive relation with the rock strata. Therefore, there is need for a channel or mat having a structure that is reinforced to resist deflection and bending under the load of the rock formation. The channel shaped support structure should be maintained in compressive relation with the surface of the rock formation by a bearing plate maintained in contact with the channel by the anchored roof bolt. The bearing plate should have a configuration that permits its installation within the width of the channel and in overlying relation with the opening in the channel. The bearing plate should have a configuration which stabilizes the bearing plate on the channel and also serves to reinforce the channel to resist deflection loads.